Battery-powered devices (e.g., consumer electronic devices, electric and hybrid automobiles, etc.) are often charged from a power source (e.g., AC power outlet) through a charging device. The charging device couples the battery to the power source through an adaptor. The cord extending between the power source and the battery-powered device can take up space. In situations where multiple battery-powered devices require charging, each with their own charger and cord, the charging area can become cramped and inconvenient.
Approaches are being developed that use over-the-air (i.e., wireless) power transmission between a transmitter and a receiver coupled to the electronic device. Wireless power transmission using an inductive coil is one method considered as an untethered method for transferring power wirelessly through a coupled electromagnetic field. In inductive wireless power transmission, power is transferred by transmitting an electromagnetic field through a transmit coil. On the receiver side, a receiver coil may couple with the transmit coil through the electromagnetic field, thus, receiving the transmitted power wirelessly.
A foreign object (e.g., metallic object) may be positioned within the near-field zone, such as between the transmitter and the receiver. As wireless power charging becomes ubiquitous and mainstream, the efficiency as well as safety aspects of wireless power transfer in the presence of foreign objects may be a concern for the end user original equipment manufacturers (OEMs).